The present invention is a process for the preparation of hydrolyzable .beta.-cyanoalkylsilanes. More particularly, this invention relates to the catalytic addition of silicon hydrides to .alpha.,.beta.-unsaturated olefinic nitriles to form .beta.-cyanoalkylsilanes. The instant process employs a catalyst comprising a diamine and copper or a copper compound. The copper or copper compound may be retained on a solid support. The process rate and yield of .beta.-cyanoalkylsilanes is increased by running the process in essentially an oxygen free environment.
Hydrolyzable .beta.-cyanoalkylsilanes are useful for the production of polyorganosiloxanes containing the .beta.-cyanoalkyl substituent. The silicon-bonded .beta.-cyanoalkyl radical is extremely resistant to hydrolysis and cleavage under hot, humid conditions. Therefore, the .beta.-cyanoalkylsilanes find particular use in the preparation of polyorganosiloxanes which must be subjected to hot humid conditions. The presence of the silicon-bonded .beta.-cyanoalkyl radical substituted on polyorganosiloxanes also tends to stabilize the polyorganosiloxanes against swelling induced by liquid hydrocarbons.
Bluestein, U.S. Pat. No. 2,971,970, issued Feb. 14, 1961, describes a method for forming cyanoalkylsilanes. The method comprises reacting a hydrolyzable silicon hydride with an .alpha.,.beta.-unsaturated olefinic nitrile in the presence of a diamine and a cuprous compound selected from the class consisting of cuprous oxide and cuprous halides.
Rajkumar et al., Organometallics 8, 550-552, 1989, describes a two-component catalyst, consisting of cuprous oxide and tetramethylethylenediamine, that promotes .beta.-hydrosilylation of acrylonitrile.
Svoboda et al., Collection Czechoslov. Chem. Commun. 38, 3834-3836, 1973, describes binary systems of a copper compound (Cu(I) oxide, Cu(I) chloride, or Cu(II) acetylacetonate) and an isocyanide (tert-butyl or cyclohexyl isocyanide) as effective catalysts for hydrosilylation of acrylonitrile by trichlorosilane and methyldichlorosilane.
The present invention improves on the prior art for .beta.-hydrosilylation of unsaturated olefinic nitriles by silicon hydrides, in the presence of a catalytic mixture of a diamine and copper or copper compound, by running the process in essentially the absence of oxygen. Removal of oxygen from the system can improve both the rate of product formation and the total yield of product from the process.